Section 7.2
Date:________________
Solving Linear Systems by Substitution
Solving a system by substitution:
1. ___________ one of the equations for ________ of its variables.
2. ________________ the expression from Step 1 into the other equation, and
_____________ for the other variable. Use _________________________!!!
3. ________________ the value from Step 2 into the result from Step 1 and
_____________.
4. _____________ the solution, an _______________________, in each of the
original equations.
Ex 1
Solve the system by substitution.
3x + y = 5
2x – y = 10
Step 1: ___________________
Substitute to find x:
Check:
Substitute to find y:
Try: Solve.
2x + 6y = 15
x = 2y
___________ is the solution to the system of equations.
Ex 2 An office supply company sells two types of fax machines. They charge $150
for one type and $225 for another type. If the company sold 22 fax machines for
$3900 last month, how many of each type did they sell?
x - __________________________
y - __________________________
Equation for the total money :______________________________________
Equation for the total number of machines sold:_________________________
The company sold _________$150-fax machines and ________ $225-fax machines.